Compact folded-waveguide resonators and filters

The paper presents a recent investigation into compact and low-loss folded-waveguide resonators and filters. The concept of folding standing waves of a TE₁₀₁ mode and a novel implementation are described with an experimental demonstration. For the filter design, an aperture coupling between adjacent resonators is introduced, which is characterised using full-wave EM simulations and verified experimentally. A demonstration two-pole folded-waveguide resonator filter of this type has been designed, fabricated and tested. Simulations and experimental results are presented to validate the design and to show the advantages of this type of filter.